Solar engines are known for producing mechanical movement in response to a mechanical unbalance in a movable structure created by received solar energy. One such engine of known construction is shown in U.S. Pat. No. 3,509,716 wherein a plurality of tanks are arranged in a circumferential path, each diametric pair of tanks being interconnected by a fluid passage. The circumferential array of tanks is disposed for rotation in a vertical plane, the tanks containing a volatile liquid. The lower tank of each diametric pair is heated by passage through a sun heated pool, while the upper tank of the diametric pair is cooled by a water spray. The volatile liquid in the heated lower tank of each diametric pair is vaporized, the volatized fluid rising through the interconnecting passage to the upper tank, which upon being cooled, causes condensation of the volatized fluid back to the liquid state. The presence of liquid in the upper tank and vapor in the corresponding lower tank causes mechanical unbalance and rotation of the circumferential structure.
Another solar powered structure providing rocking motion or rotary motion is shown in U.S. Pat. No. 1,911,456 in which one or more pairs of bulbs are in fluid interconnection and contain a volatile liquid. One bulb of each pair is shaded from solar energy, while the other of the bulbs is exposed to such energy. The unshaded bulb becomes heated and forces the liquid therein via the interconnecting passage to the opposite bulb which now contains a greater quantity of liquid and therefore causes a mechanical unbalance. In the known apparatus described above, a volatile liquid must be employed as the operative fluid and the movable structure requires one or more pairs of opposed vessels containing the volatile liquid and being in fluid interconnection. The required interconnection of opposed pairs of vessels tends to complicate the design of a practical engine structure.